Recently I purchased a black hills spruce and a prince blue holly, both in 5 gallon containers.
When is the best time to plant these? Where is the best place, and what is the best way to plant them? Should I leave them in the containers outside until spring and then plant?
Right now there is no snow and we are having a mild winter. (so far)

The plants will winter better planted in the ground where their roots are insulated than they will in the containers above ground, so plant them as soon as possible! For the record, most evergreens (especially those in ball and burlap) are best purchased and planted in early spring, but container grown stock can be planted any time the ground is workable -- meaning not frozen and not too muddy.